Review: http://www.nature.com/nrn/journal/v7/n7/full/nrn1950.html
Endogenous cannabinoids belong to a group of fatty acid amines, the N-acetylethanolamines (NAEs). Biochemical evidence indicates that endogenous NAEs are produced and released by animal and human neurons, and by human epidermal keratinocytes. On local application, cannabinoids have analgesic and antipruritic effects in acute pain and itch models; moreover, there is growing evidence for the suppression of itch by topical cannabinoid receptor agonists under clinical conditions. Direct activation of CB1 and CB2 (but also activity at TRPV1), a new cannabinoid-receptor 'CB2-like receptor' and non-receptor-mediated effects are discussed as possible itch-suppressing mechanisms.
In Germany a product with N-palmitoylethanolamine (PEA, palmidrol, N-(2-hydroxyethyl) hexadecanamide) is already on the market (Physiogel A.I.), prescription free.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Search&db=pubmed&term=+%22Topical+cannabinoid+agonists%22&tool=QuerySuggestion
http://www.physiogel.info/de/physiogel_ai_creme.htm
Physiogel A.I. helps very well against refractory itching , I have own experience with it.
I do not know if a PEA-product is available in the US too. Is it? However, the review is worth to read it, although you need some medical knowledge to understand it.
Regards, Drofi